Marketing a Directory for Specialists and Professionals

[ECommerceConversions]

Hey Guys, got a question about this one and maybe some advice if you're up to it, especially if you got experience with this. I'm considering creating a directory where people of a certain specialty can pay for and be included. Realistically, it would be nation wide with local regions. Now, this would really be targeted to brick and mortar businesses, and the traffic to the directory for their leads would come from a combo of google/overture as well as SEO. Here's the main question:

Is it feasible to use telemarketing/other telemarketers in order to call up all these specialists to get them to enlist. Do you think a flat fee would be the best approach, since it is simpler for non-techie internet people to understand. Or maybe, a pay per lead system where they contact the company via my servers (however that makes it riskied for me and the conversion rates)

So, any thoughts on telemarketing or how to set all this up? You guys are the best at this stuff.